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Emerging growth company ☒

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Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class

Trading Symbol(s)

Name of Each Exchange on Which Registered

Common Stock, par value $0.001

ALLK

The Nasdaq Global Select Market

Item 8.01 Other Events.

On August 5, 2019, Allakos Inc. (the “Company”) hosted a conference call and webcast to present detailed results from its Phase 2 trial in Patients with Eosinophilic Gastritis and/or Eosinophilic Gastroenteritis. A copy of the presentation is filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Disclaimer This presentation contains forward-looking statements. All statements other than statements of historical fact contained in this presentation, including statements regarding the financial position of Allakos Inc. (“Allakos,” the “Company,” “we” or “our”); the generation of future value; business strategy; plans and objectives for future operations; our expectations regarding the potential benefits, activity, effectiveness and safety of our product candidates; our expectations with regard to the initiation, design, timing and results of our clinical studies, preclinical studies and research and development programs, including the timing and availability of data from such studies; our preclinical, clinical and regulatory development plans for our product candidates, including the timing or likelihood of regulatory filings and approvals for our product candidates; the size of the market opportunity for our product candidates in the diseases we are targeting; and our expectations with regard to our ability to acquire, discover and develop additional product candidates and advance such product candidates into, and successfully complete, clinical studies, are forward-looking statements. Allakos has based these forward-looking statements on its estimates and assumptions and its current expectations and projections about future events. The words ‘‘anticipate,’’ ‘‘believe,’’ ‘‘continue,’’ ‘‘could,’’ ‘‘estimate,’’ ‘‘expect,’’ ‘‘intend,’’ ‘‘may,’’ ‘‘plan,’’ ‘‘potential,’’ ‘‘predict,’’ ‘‘project,’’ ‘‘target,’’ ‘‘should,’’ ‘‘would,’’ and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. The Company may not actually achieve the plans, intentions, or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. The forward-looking statements included in this presentation speak only as of the date of this presentation and are subject to a number of risks, uncertainties, and assumptions, including, but not limited to: the Company’s early stages of clinical drug development; the Company’s ability to timely complete clinical trials for, and if approved, commercialize AK002, its lead compound; the Company’s ability to obtain required regulatory approvals for its product candidates; uncertainties related to the enrollment of patients in its clinical trials; the Company’s ability to demonstrate sufficient safety and efficacy of its product candidates in its clinical trials; uncertainties related to the success of later-stage clinical trials, regardless of the outcomes of preclinical testing and early-stage trials; market acceptance of the Company’s product candidates; uncertainties related to the projections of the size of patient populations suffering from some of the diseases the Company is targeting; the Company’s ability to advance additional product candidates beyond AK002; the Company’s ability to obtain additional capital to finance its operations; and other risks described in the “Risk Factors” section included in our periodic filings that we have made and will make with the Securities and Exchange Commission (“SEC”). In addition, Allakos operates in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for Allakos’s management to predict all risks, nor can Allakos assess the impact of all factors on its business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements that Allakos may make. In light of these risks, uncertainties and assumptions, the forward-looking events and circumstances discussed in this presentation are inherently uncertain and may not occur, and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. Accordingly, you should not rely upon forward-looking statements as predictions of future events. Allakos does not undertake any obligation to update or revise any forward-looking statements, to conform these statements to actual results or to make changes in Allakos’ expectations, except as required by law. Accuracy of Data: This presentation contains statistical data based on independent industry publications or other publicly available information, as well as other information based on Allakos’s internal sources. We have not independently verified the accuracy or completeness of the data contained in these industry publications and other publicly available information. Accordingly, Allakos makes no representations as to the accuracy or completeness of that data. Additional Information:The Company has filed and will file Current Reports on Form 8-K, Quarterly Reports on Form 10-Q, and Annual Reports on Form 10-K, and other documents with the SEC. You should read these documents for more complete information about the Company. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. This presentation concerns products that are under clinical investigation and which have not yet been approved for marketing by the U.S. Food and Drug Administration. It is currently limited by federal law to investigational use, and no representation is made as to its safety or effectiveness for the purposes for which it is being investigated.

Safety Summary Generally well tolerated Most common AE was mild to moderate infusion related reactions (IRR) 60% of AK002 patients vs 23% placebo 93% mild to moderate (flushing, feeling of warmth, headache, nausea, dizziness) Mostly on first infusion, greatly reduced or does not occur on subsequent infusions 1 drug-related serious adverse event, an IRR which recovered within 24 hours with no further sequelae Treatment-emergent SAEs: 9% on AK002, 14% on Placebo No other significant AEs

Open-Label Extension & Next Steps

Extension Study Status 92% of patients elected to enter long-term extension study Current median duration of treatment 3 months Efficacy appears to improve with continued dosing Optimizing dose administration Pre-dose with oral prednisone 1 day prior to first and second AK002 doses No IRRs observed in patients using steroid pre-dose Allows administration of 1mg/kg as first dose Infusion time can be reduced to < 2 hours on second and subsequent doses